Transformer oil



'- Patented Dec. 15, 1931 UNITED STATES PATENT OFFICE OADBELL B. MCGULLOUGH AND RUSSELL L. JENKINS, F ANNISTON, ALABAMA, AS-

SIGNOBB, BY MESNE ASSIGNMENTS, TO SWAN N RESEARCH, INC 01' BIRMINGHAM, ALABAMA, A CORPORATION OF ALABAMA mom on Io Drawing.

This invention relates to a new insulating di-electric liquid and particularly to a liquid in which electrical conductors-may be immersed. It is particularly adapted to be 5 used as a filling material for oil immersed transformers. i

At present, mineral oils are used to fill transformers, which oils, however, are objectionable in that they tend to form sludges which must be removed by filtration from time to time. Furthermore, the have a relatively low flash oint, which ma es the product something 0 a fire hazard.

Another product which has been propose is a mixture of diphenyl oxide and carbon tetrachloride. This material, however, has a relativel hi h freezing point and consequently is isa vantageous when used in cold weather. V

We have found that several of the lower 1 chlorinated diphenyls can be used advantageously and the above difliculties largely overcome. For example, we have found that when a mixture is made containing approximately 75% of 2-chlorodiphenyl (ortho) and 25% 4-chlorodiphenyl (para), a eutectic mixture is obtained which has a freezing point at 14 C. It has a flash point at 127 to 129 C., and a fire point at 200 C.

The freezing point of the above mixture may be lowered to a point considerabl below 0 C. in the followin manner ake 55% of the above mixture o chloro-diphenyls and mix it with 45% of a product obtained g in the following manner:

Chlorinate diphenyl, using iron as a catalyst, until it reaches a specific gravity of 1.379 at 20 C. This corresponds to a chlorine content in the neighborhood of 42% by weight. The product is washed with dilute hydrochloric acid, then with water, and finally with soda ash toneutralize acidity, and dried. The entire charge is then distilled at atmospheric pressure, no attempt being made 5 to separate any fraction.

Application filed October as, 1929. Serial 110. 408,118.

On mixing the product with the mixture given above it will be found to have the following properties:

Denslty 1. 246 at 25 C.

Visc0slty 45 seconds Saybolt at 37.8 C. solidifies minus 30 C. Flash point (5 sec.) 140 C.

Flame point 218 C.

The density of the oil may vary somewhat dependin upon how far the chlorination is carried, or example it may vary between 1.22 and 1.28 at 25 C. A higher chlorine content will also increase the viscosity which we have found to vary between 40-50 seconds at 37.8 C.

While the proportions given above will give a satisfactory oil of the properties shown above, it should be realized that other proportions are possible and may be desirable for certain particular uses.

What we claim is:

1. A dielectric comprising a liquid mixture of chlorinated diphenyl having a solidification point below 14 C. i

2. A dielectric comprising a mixture of orthoand para-chlorodiphen 1, having a solidification point in the neig borhood below 14 C. and a flash point above 127 C.

3. A dielectric comprising a mixture of ortho and para-chlorodiphenyl in the eutectic proportions.

4. A dielectric comprising a liquid mixture of orthoand parawith a higher chlorinated diphenyl, said liquid mixture having a solidificatgm point in the neighborhood of minus 30 5. A dielectric comprising a liquid mixture of 55% of the eutectic mixture of ortho-and para-chlorodiphenyl with 45% of an oil formed by chlorinating diphenyl to a specific gravity of 1.379 at 20 'C.

6. A dielectric comprising a distilled substance of substantially 41.25% ortho-chlorodiphenyl, 13.75% para-chlorophenyl and 45% of a product formed by chlorinatingflo 2 "a I I diphenyl to a density in the neighborhood of 1.379 at C.

7. A dielectric comprised of chlorinated diphenyl having a. density between 1.22 and 1.28.

8. A dielectric comprised of chlorinated diphenyl, havin a density in the neighborhood of 1.25 an a flash point in the neighborhood of 140 C. 10

,1 A dielectric comprising a liquid chlorinated diplienyl.

In testimony whereof we afiix ou'r signa' tures.

RUSSELLLI JE 0AM" PMBE'LL' RIMcciJLL" ()UGH. Y

NKINS. v 

